Conventionally, there have been known power modules in which a power chip including a semiconductor device such as Insulated Gate Bipolar Transistor (IGBT) is mounted on a leadframe therein, and of which the whole system thereof is molded with resin. Since such a semiconductor device produces heat during an operating state, it is common to dispose a heat sink via an insulating layer on a back side surface of the leadframe in order to cool the semiconductor device.
When such a power module is attached to a cooling body, e.g. the heat sink in this way, a liquid thermal compound is coated to a metal surface (surface of a leadframe) facing (opposed to) the cooling body, and one surface or both surfaces of the cooling body facing (opposed to) the metal surface. Thus, a gap due to roughness, such as surface cracks etc. and a warpage can be filled up with the thermal compound.